A battalion composed of troops from Sudan's northern and southern armies is set to deploy Tuesday to the disputed Abyei area on the country's north-south border.  As Derek Kilner reports for VOA's East Africa bureau in Nairobi, fighting last month displaced tens of thousands, raising concerns about the prospects of a 2005 peace agreement.

The battalion of more than 750 soldiers will be drawn equally from the northern Sudan Armed Forces and the southern Sudan People's Liberation Army, according to the vice president of the semi-autonomous southern government, Riek Machar.  The battalion will be commanded by the SPLA's Valentino Tocmac, while the deputy commander will be from the north. 

The deployment of the so-called joint integrated units is part of an agreement on Abyei signed last week by Sudanese President Omar al-Bashir and southern President Salva Kiir, who also serves as vice president in the national unity government. 

According to U.N. estimates, several days of fighting between northern and southern troops last month displaced tens of thousands from Abyei town, and left at least 60 dead.   

Under the agreement, northern and southern troops that are not part of the joint units will be withdrawn from Abyei; an interim administration will be put in place, with a head from the south and deputy from the north; and a police force drawn from the local population will begin patrols. 

The agreement calls for the removal of restrictions on the movement of U.N. peacekeepers, and the resettlement of those displaced by last month's clashes.  Southern Vice President Riek Machar says the latter task is a top priority.

"It is urgent for the civilian population to go back, those who were displaced from Abyei.  And it is the start of the rainy season," said Machar.

Abyei, which contains much of Sudan's oil, has long been a stumbling block in implementing the 2005 Comprehensive Peace Agreement, which ended a two-decade civil war.

The agreement set up an international commission to determine the boundaries of the area, but its findings were rejected by President Bashir.  As part of last week's deal, the two sides agreed to seek international arbitration to determine the boundaries.   Northern and southern officials are set to meet in the southern capital Juba on Friday to discuss the choice of an arbitrator. 

The two sides have agreed in the past to many of the measures in the 2005 agreement, including the establishment of joint military units, with little result.  But Machar, a member of the Sudan People's Liberation Movement, says he is optimistic about the prospects this time around.

"It has been challenging, I believe the two parties are committed to that agreement and it will be implemented," added Machar.  "As for SPLM we are committed to it, we will implement our bit and hopefully the National Congress will do the same."

Residents of Abyei are set to vote in 2011 on whether to join the south or the north, at the same time as the south holds a referendum on whether to secede from north.  

Analysts say the recent dispute over Abyei presented the greatest threat yet to the north-south peace agreement.  South African President Thabo Mbeki will discuss the progress of the agreement with Sudanese leaders Tuesday in Khartoum and Wednesday in Juba.